This application is based upon and claims the benefit of priority from Japanese patent application No. 2006-223596, filed on Aug. 18, 2006, the disclosure of which is incorporated herein in its entirety by reference.
The present invention relates to tape carriers, tape carriers for liquid crystal display devices, and liquid crystal display devices, in particular, to a tape carrier, a tape carrier for liquid crystal display device, and a liquid crystal display device in which breakage of signal lines is prevented and durability is enhanced.
In the tape carrier with a configuration in which a driver IC is resin sealed on the tape carrier and the length between an input terminal and an output terminal is short, for example, when the connection between a glass substrate on the liquid crystal display side and a circuit substrate on the drive circuit side is a planar connecting state, a phenomenon occurs in which wrinkles form in the tape carrier when returning from high temperature to normal temperature due to the difference in expansion coefficients caused by heat of when the glass substrate and the circuit substrate are connected.
When ambient temperature changes with the wrinkles formed, the signal lines may break due to such wrinkles. In this case, the accident of signal line breakage, in particular, is known to occur frequently at the edge portion of a resin applying region for resin sealing the driver IC near the ends in the longitudinal direction of the driver IC (i.e., region of both ends shifted from the signal line group of input signal lines and output signal lines on the tape carrier), that is, near the boundary of the portion applied with resin and the portion not applied with resin.
As related arts generally known for preventing breakage of signal lines on the tape carrier include the followings.
Japanese Laid-Open Patent Publication No. 2002-124544 (Patent document 1) relates to preventing breakage of a terminal for connecting the driver IC and the tape carrier, that is, an inner lead terminal, and relates to preventing breakage at solder resist edge of the inner lead caused by the difference in expansion coefficients of the materials of the tape carrier. In this case, the inner lead is a distal end portion of the signal line connecting with the terminal of the driver IC, such portion being the portion of the signal line arranged in the vicinity of the driver IC and not covered with the solder resist, and the configuration thereof is disclosed in patent document 1 as the signal line arranged in the resin applying region.
In the liquid crystal display device in which an LCD (Liquid Crystal Display) panel and a circuit substrate are connected by way of a TCP (Tape Carrier Package) serving as a driver IC arranged on a base film, the circuit substrate is supported with the TCP bent downward during transportation. In this case, a phenomenon in which a predetermined region of the TCP repetitively is twisted by the floating of the circuit substrate occurs.
In response to such situation, Japanese Laid-Open Patent Publication No. 11-204588 (patent document 2) discloses a configuration including a reinforcement device for preventing disconnection in a predetermined region at both ends of the base film, so that the input/output lead wires at both ends in the width direction of the TCP are prevented in advance from breaking (disconnecting) over time. The reinforcement device is configured with at least two or more common signal leads and a dummy lead connected to each other in the width direction of the base film, or with such common signal leads and dummy lead coupled together. In this case, the region of the reinforcement device is between the bent portion of the base film that is bent in correspondence to the edge of the LCD panel and the input/output lead, or between the bent portion and the driver IC. That is, patent document 2 discloses an example of a technique for preventing breakage related to the input/output lead.
In press working the tape carrier, distortion from bend or tension is generated by the gap formed between a die and the base film, which may deform or break the tape carrier. In view of such issue, Japanese Laid-Open Patent Publication No. 08-160446 (patent document 3) discloses a configuration in which a conductor is arranged on both sides in the extending direction of a conductor pattern, where a dummy conductor pattern with the same thickness as such pattern is arranged. That is, patent document 3 discloses an example of a technique for preventing deformation and breakage of the tape carrier.
Japanese Laid-Open Patent Publication No. 06-301047 (Patent document 4) discloses a tape carrier with a slit formed in the tape carrier body and a bendable configuration, where an electrically isolated dummy pattern is arranged extending parallel to the signal line group while covering a longitudinal end of the slit and the base film at the periphery of such end on the outer side of the signal line groups so that the signal lines at the slit portion does not break by the bending stress when the signal line group output from the driver IC is bent at the slit (without lining) portion into a substantially U-shape. That is, patent document 4 discloses an example of a technique for preventing breakage of the slit portion without lining (i.e., with base film cut).
However, disclosure on countermeasures for breakage of wiring pattern that occurs at the edge of the resin applying region, which is being addressed in the present invention, is not made in the techniques disclosed in the patent documents described above. The breakage of the pattern that occurs at the edge of the resin applying region which is a problem will be described with reference to the drawings.
FIG. 5A shows a tape carrier, which is a main component of a tape carrier package for liquid crystal display device. The tape carrier (also referred to as “TAB tape”) 100 is configured by an insulation film tape 101, which is a base film; input signal lines 106 and output signal lines 107 wired on the insulation film tape 101; a driver IC 102; a resin applying region 105 of resin filled at a portion on which the driver IC 102 is mounted; and an input terminal 103 and an output terminal 104.
The tape carrier 100 connected to a glass substrate 202 and a circuit substrate 201 is shown in FIG. 5B. A conductor surface of the tape carrier 100 shown in FIG. 5B is on the back side of the figure.
In FIG. 5B, when the length between the input terminal 103 and the output terminal 104 of the tape carrier 100 is short, wrinkles 110 is formed in the tape carrier 100 positioned at an intermediate position of the glass substrate 202 and the circuit substrate 201 due to the difference in expansion coefficients of each member after the glass substrate 202 and the circuit substrate 201 are connected, or wrinkles 110 is formed in the tape carrier 100 by positional shift which is occurred when the glass substrate 202, the circuit substrate 201, and the tape carrier 100 are assembled to the liquid crystal display device.
Such wrinkles 110 tend to be concentrated at non-continuous portion of strength of the tape carrier 100. Such non-continuous portion is positioned at the edge portion of the resin applying region 105 (the portion near the boundary of the portion applied with resin and portion not applied with resin, which is the portion where resin is not applied and the strength is weak) where is the position of the outermost signal lines of the signal line group of the input signal lines 106 and the output signal lines 107. That is, the non-continuous portion is positioned at both edges of the input signal lines 106 and the output signal lines 107, and corresponding to the boundary region 109 at both edges of the input signal lines 106 and the output signal lines 107.
When stress changes due to mechanical impact or change in ambient temperature in such state, bending movement occurs at the portion of wrinkles 110, and cracks are caused by such bending at the edge portion of the resin applying region 105, which is the non-continuous point of strength of the tape, and at the portion of the signal lines at both edges of the input signal lines 106 and at both edges of the output signal lines 107 (e.g., signal lines wired in the boundary region 109 shown in FIG. 5B), and the signal lines at the relevant portion breaks finally.